Double-loop Reentry in the Left Atrium with a Shared Mid-Diastolic Isthmus in a Non-surgical Patient with Left Atrial Scarring: a More Common than Expected Arrhythmia?

Abstract

This is an 80-year-old female patient with dilated cardiomyopathy and poor left ventricular function (ejection fraction 25%) as well as moderate mitral regurgitation. Prior coronary angiography showed no critical stenosis. Four years earlier, she had experienced episodes of persistent atrial fibrillation, thus worsening her congestive heart failure. After cardioversion, oral amiodarone prevented recurrences of atrial fibrillation in the following years. In the months before the current procedure, while still on amiodarone, the patient complained again of palpitations. Persistent atrial tachycardia with a cycle length of 300 ms and 2:1 atrioventricular conduction with left bundle branch block was documented. Since the arrhythmia recurred after electrical cardioversion and caused worsening of her clinical conditions, the patient was referred for ablation, in spite of her age. Before the procedure, an intravenous bolus of adenosine helped identify the surface P wave morphology, which showed diffuse low voltage (Fig. 1) and was positive in V1-V4, biphasic (−/+) in the inferior leads and flat in all other leads.